define([], function() {

    'use strict';

    /**
     * Describes the root top-level ABCS page view model.
     *
     * Each ABCS page binds its view to an instance of generated <code>PageViewModel</code>
     * representing the root page view model. ABCS uses {@link http://knockoutjs.com/documentation/introduction.html knockout} to bind
     * HTML view t its model.
     *
     * The model consists of higher constructs such as page {@link viewmodel/js/api/Archetype Archetypes},
     * Business Objects ({@link entity/js/api/Entity Entities}) the page works with
     * and generated Business Methods used on the page.
     *
     * Page view model instance:
     * <ul>
     * <li>is accessible as <code>$root</code> context inside the DOM generated
     * for the page</li>
     * <li>passed as <code>self</code> into Custom JS Business Action code blocks</li>
     * <li>passed as <code>params.root</code> into Custom Code component view model</li>
     * </ul>
     *
     * @AbcsAPI stable
     * @exports viewmodel/js/api/PageViewModel
     * @constructor
     * @private
     * @version 16.3.5
     *
     * @example <caption>Pass page view model into custom ko component's model</caption>
     * <my-custom-component params="{
     *     pageViewModel: $root
     * }"></my-custom-component>
     * @example <caption>List page Business Objects in custom component's model</caption>
     * var MyCustomComponentModel = function (params) {
     *     // params.pageViewModel contains reference to the page view model
     *     // as the previous example demonstrates
     *     var pageViewModel = params.pageViewModel;
     *
     *     // build list of all BO names used on the page
     *     var entities = pageViewModel.Entities;
     *     var message = 'Page contains Business Objects: ';
     *     message = message +
     *     Object.keys(entities).map(function (entityId) {
     *         return entities[entityId].getName();
     *     }).join(', ');
     *
     *     // set the message into a ko observable to be bindable in your
     *     // component's HTML view
     *     this.message = ko.observable(message);
     * };
     */
    var PageViewModel = function() {
    };

    /**
     * Map of all {@link viewmodel/js/api/Archetype archetypes} used on the page
     * identified by their ids.
     *
     * <strong>Note that</strong> particular archetypes may not be forever present
     * on a page. As their owner component (such as table, list or a form) may be
     * removed from the page, so may the archetype be removed along with it. Hence
     * you should always check for the archetype's existence before using it.
     *
     * @AbcsAPI stable
     * @version 16.3.5
     * @type {Object<String, viewmodel/js/api/Archetype>}
     */
    PageViewModel.prototype.Archetypes = {};

    /**
     * Map of all Business Objects ({@link entity/js/api/Entity Entities}) used
     * by page archetypes identified by their ids.
     *
     * @AbcsAPI stable
     * @version 16.3.5
     * @type {Object<String, entity/js/api/Entity>}
     */
    PageViewModel.prototype.Entities = {};

    /**
     * Map of all observables objects provided by page archetypes. Contains all
     * objects returned by {@link viewmodel/js/api/Archetype#getObservables Archetype.getObservables}
     * identified by {@link viewmodel/js/api/Archetype#getId archetype ids}.<br>
     * So <code>pageViewModel.Observables.customerTableArchetypeId</code>
     * is a shortcut for <code>pageViewModel.Archetypes.customerTableArchetypeId.getObservables</code>.
     *
     * @AbcsAPI stable
     * @version 16.3.5
     * @type {Object<String, Object>}
     * @see {@link viewmodel/js/api/Archetype#getObservables Archetype.getObservables}
     */
    PageViewModel.prototype.Observables = {};

    /**
     * Initialize page using given contextual data. This method is always called
     * after first creation of the page.
     *
     * @param {ContextualData} contextualData
     */
    PageViewModel.prototype.create = function(/*contextualData*/) {
    };

    /**
     * Update existing page using contextual data. When applicaito navigation is
     * returning to previous opened page this method is called instead create().
     *
     * @param {ContextualData} contextualData
     */
    PageViewModel.prototype.update = function(/*contextualData*/) {
    };

    /**
     * Returns textual short representation of this page which can be used to
     * bookmark this page. Reopening page fromj bookmark will result in this
     * string being passed into above create method using contextual data of
     * type Bookmark.
     *
     * @returns {String}
     */
    PageViewModel.prototype.getBookmark = function() {
    };

    /**
     * Returns display name of the page.
     * <p>
     * This information is leveraged in the browser's TITLE in the generated
     * application and can be uptaken by components of the page.
     *
     * @returns {String}
     */
    PageViewModel.prototype.getDisplayName = function() {
    };

    return PageViewModel;

});